News from Nanotechjapan


Successful Development of World's First Vertical Ga2O3 Transistor through Low-Cost, Highly-Manufacturable Ion Implantation Doping Process

 On December 12, 2018 National Institute of Information and Communications Technology (NICT), and Tokyo University Agriculture and Technology (TUAT) announced that research team led by Dr. Masataka Higashiwaki, Director of Green ICT Device Advanced Development Center, Advanced ICT Research Institute, NICT had succeeded in developing vertical Ga2O3 metal-oxide-semiconductor field-effect transistors (MOSFETs) by N- and Si-ion implantation doping process. This work was partially supported by Council for Science, Technology and Innovation (CSTI), Cross-ministerial Strategic Innovation Promotion Program (SIP) supervised by the New Energy and Industrial Technology Development Organization (NEDO). The result of the research was published in IEEE Electron Device Letters*.

 Power electronics is a key technology for efficient regulation and conversion of electric power in systems such as electric vehicles and power grids. In contrast to SiC and GaN currently employed, Dr. Higashiwaki perceived that Ga2O3 is a promising candidate of materials for power devices, owing to its larger bandgap. His success in demonstrating Ga2O3 MOSFETs with the lateral structure, that is, electrodes of source, gate and drain aligned on the surface, has induced many researchers to work on Ga2O3 power devices. However, lateral power devices tend to require large area owing to wide gate-to-drain separation required for high breakdown voltage. In contrast, vertical MOSFETs are preferred for reduced chip size, where current is induced with gate voltage under dielectric layer between two n-type source regions on the surface, and is driven through the space between two p-type current blocking regions down to drain.

 The research team developed p-type ion implantation doping process using nitrogen (N), in addition to previously developed n-type process using silicon (Si). Depletion-mode vertical Ga2O3 MOSFETs were successfully realized applying developed ion implantation processes to form source and current blocking regions. The transistors exhibited a drain current density of 0.42 kA/cm2, a specific on-resistance of 31.5 mΩ·cm2, and an output current on/off ratio of over 108.

 The team expects this success will open the way for new generations of low-cost and highly-manufacturable power electronic devices using Ga2O3

*Man Hoi Wong, Ken Goto, Hisashi Murakami, Yoshinao Kumagai, and Masataka Higashiwaki, "Current Aperture Vertical β-Ga2O3 MOSFETs Fabricated by N- and Si-Ion Implantation Doping",. IEEE Electron Device Letters, Early Access, DOI: 10.1109/LED.2018.2884542; Date of Publication: 03 December 2018